JP4480090B2 - Coated tool - Google Patents

Description

  The present invention relates to a coated tool, and more particularly to a tool coated with a coating containing zirconium.

  In general, a coated tool is produced by forming a hard film on the surface of a substrate made of super hard alloy, high speed steel, or special steel by chemical vapor deposition or physical vapor deposition. Such a coated tool has both the wear resistance of the coating and the toughness of the substrate, and is widely put into practical use. Generally, when cutting a hard material at high speed without using a cutting fluid (hereinafter referred to as dry cutting), the cutting edge temperature of the cutting tool rises to around 1000 ° C. Cutting tools need to withstand mechanical impacts caused by wear and intermittent cutting due to contact with the work material in such a high temperature environment, and coated tools that have both wear resistance and toughness are useful. . The hard film includes a film made of carbide, nitride, carbonitride, carbonate, nitride oxide, carbonitride oxide of periodic table 4, 5, and 6 metal having excellent wear resistance and toughness. A coated tool in which an aluminum oxide film excellent in oxidation resistance is coated as a single layer or a multilayer film is generally used. Moreover, titanium, especially its carbide (TiC), nitride (TiN), and carbonitride (TiCN) are mainly used for said periodic table 4, 5, 6 metal. For this reason, hereinafter, in order to avoid complications, titanium will be specifically described in detail as a representative of Group 4, 5, and 6 metals of the periodic table.

  These TiC, TiN, and TiCN films have very high Vickers hardness Hv of about 3200, 2100, and 2700 at room temperature, and are excellent in wear resistance at room temperature. However, since the hardness of these films rapidly decreases as the temperature rises, there is a problem that the wear resistance is drastically reduced in dry cutting in which the temperature of the cutting edge reaches around 1000 ° C. In order to improve the wear resistance of these hard films, there has been proposed a method (Japanese Patent Publication No. 11-510856) for coating a tool substrate with a film such as titanium zirconium carbonitride. This method is a method in which a carbonitride film containing at least two kinds of metal elements is coated by a CVD method using a CN compound gas. The resulting titanium zirconium nitride carbonitride film had a large crystal grain size and was not necessarily satisfactory in terms of wear resistance and chipping resistance as a tool.

As a result of diligent research to solve the drawbacks of the above-described prior art coated tools, the present inventors have determined that hard films containing zirconium and titanium as metal components, such as (Ti, Zr) ) When a specific condition is satisfied in a CN film or (Ti, Zr) CNO film, etc., a film with excellent film adhesion and wear resistance is realized without a sharp decrease in film hardness even at high temperatures. We found out what can be done, and first, Japanese Patent Application No. 2001-11632, Japanese Patent Application No. 2001-170804, Japanese Patent Application No. 2000-394137, Japanese Patent Application No. 2000-396568, Japanese Patent Application No. 2001-3044, Japanese Patent Application No. 2001-3060, Japanese Patent Application This application was disclosed as 2001-23821. As a tool coated with a hard film containing both zirconium and titanium, a cutting tool (Patent Document 1) recently coated with a mixed layer of titanium carbonitride crystal grains having a granular crystal structure and zirconium carbonitride crystal grains has been proposed. However, in the mixed layer, TiCN and ZrCN individually form crystal grains, and Ti, Zr, C, and N are not formed from the integrated crystal grains. For this reason, it is not possible to solve the drawbacks of the film hardness reduction of TiCN crystal grains at high temperatures and the lack of film hardness of ZrCN crystal grains at room temperature, or because the bonding force between these crystal grains is not sufficient. The wear resistance and chipping resistance obtained are not always satisfactory.

The present invention further develops the above-described invention previously proposed by the inventors of the present application, that is, an invention related to a hard film containing zirconium and titanium as metal components, and crystal grains in a film containing zirconium and titanium. It is to provide a coated tool that has excellent cutting durability characteristics as compared with the prior art by enhancing the strength of the field (twinning) and the film adhesion between the upper Zr (CN) film (continuous twinning). .

That is, the present invention provides the substrate surface with any one of the groups 4, 5, and 6 of the periodic table and aluminum carbide, nitride, oxide, carbonitride, carbonate, nitride oxide and carbonitride oxide. It has a layer coating or two or more types of multilayer coatings, and at least one of the coatings contains zirconium and titanium. The coating containing zirconium and titanium is composed of a titanium carbonitride film in the lower layer and Zr (CN) in the upper layer. A film is coated , the film containing zirconium and titanium, the Zr (CN) film contains crystal grains having a twin crystal structure , and the twin boundary portion of the Zr (CN) film contains the zirconium and titanium. It is a coated tool characterized by being continuous from the twin boundaries of the coating film it contains . In the coated tool of the present invention, since the coating containing zirconium and titanium has a twin structure, the strength of the grain boundary is high, and good cutting durability characteristics are realized.

  As described above, by applying the present invention, it is possible to realize a useful zirconium-containing film-coated tool having excellent cutting durability characteristics and excellent crystal grain boundary strength and adhesion to the upper layer film of the zirconium-containing film. Can do.

In the coated tool of the present invention, it is preferable that a layer containing crystal grains having a twin crystal structure is formed on the upper Zr (CN) film containing zirconium and titanium . When the upper layer Zr (CN) contains crystal grains having a twin crystal structure, the grain boundary strength in the upper layer is increased, and further excellent cutting durability characteristics are realized. In the coated tool of the present invention, it is preferable that the twin boundary portion of the upper Zr (CN) layer is continuous from the twin boundary portion of the coating containing zirconium and titanium . Since the twin boundaries are continuous, the film containing zirconium and titanium and the Zr (CN) layer formed thereon are continuously formed at the crystal lattice plane level. High adhesion between the layers is realized, and since both layers have a twin crystal structure, the strength of the crystal grain boundary of each layer itself is high, and further excellent cutting durability characteristics are realized. This effect is particularly pronounced when two or more zirconia-containing films are formed as a multilayer film.
In the coated tool of the present invention, it is preferable that a twin boundary portion (twin plane) constituting the twin structure is composed of {111} planes. The twin boundaries constituting the twin structure are composed of {111} planes having many lattice points, so that the twin boundaries are densely formed and between the crystal grains in contact with the twin boundaries as a boundary. It is judged that the grain boundary strength is further increased and further excellent cutting durability characteristics can be obtained.

In the coated tool of the present invention, the Zr (CN) film is preferably grown epitaxially from a film containing zirconium and titanium . By doing so, excellent adhesion between both layers can be obtained, and further excellent cutting durability characteristics can be obtained. In the coated tool of the present invention, titanium is represented as a representative of Group 4, 5, and 6 metals of the periodic table, and other similar metals such as Zr, Hf, V, Nb, Ta, Cr, Mo, W In either case, substantially the same effect can be obtained. The film containing zirconium and titanium is not limited to a TiZrCN or TiZrCNO film, but may be a TiZrC, TiZrCO, TiZrN, or TiZrNO film. A TiZrCN film or a TiZrCNO film is formed by reacting CH ₃ CN and TiCl ₄ or CH ₃ CN and TiCl ₄ with an oxidizing gas (for example, CO ₂ or CO alone gas or CO ₂ and CO mixed gas). The film is not limited to a film, but may be a TiZrCN film or a TiZrCNO film formed by reacting CH ₄ , N ₂ , TiCl ₄ , CH ₄ , N ₂ , TiCl ₄ and an oxidizing gas. Further, the film containing zirconium and titanium is not limited to the above film, and for example, one or two of Cr, Hf, Ta, Nb, Mg, Y, Si, B, W, Mo, S may be added to the above film. A film added with 0.3 to 10% by mass of the above may also be used. If the amount is less than 0.3% by mass, the effect of adding these does not appear. If the amount exceeds 10% by mass, the effect of wear resistance and high toughness of the film becomes low.

The coating containing zirconium and titanium , the titanium carbide layer, the titanium carbonitride layer, the titanium carbonate layer, and the aluminum oxide film that can constitute the coated tool of the present invention are not necessarily the outermost layer. For example, at least one layer of titanium, zirconium, or hafnium compound (for example, TiN, ZrN, HfN, TiCN layer, ZrCN, HfCN, or a multilayer film combining these) may be further coated thereon. The film is allowed to contain, for example, several mass% of inevitable additives and impurities as long as the cutting durability characteristics of the coated tool of the present invention are not deteriorated. For the production of the coated tool of the present invention, a known film forming method can be adopted. For example, a normal chemical vapor deposition method (thermal CVD), a chemical vapor deposition method with plasma (PACVD), an ion plating method, or the like can be used. The application is not limited to cutting tools, but may be wear-resistant materials, molds, molten metal parts, etc. coated with a hard film. Next, although the coated tool of this invention is demonstrated concretely by an Example, this invention is not limited by these Examples.

Example 1
A film formation temperature of 900 by a thermal CVD method on a cemented carbide throwaway chip having a composition of WC: 80% by mass, TiC: 5% by mass, (Ta, Nb) C: 6% by mass, and Co: 9% by mass. First, a titanium nitride film having a thickness of 0.4 μm was formed at a temperature of 0 ° C. Subsequently, CVD is performed with a source gas composed of 850 ° C., TiCl 4 gas: 1.5 vol%, CH 3 CN gas: 1.0 vol%, N 2 gas: 45 vol%, and the remaining H 2 carrier gas per minute. A titanium carbonitride film having a thickness of 1 μm was deposited at a deposition pressure of 5.0 kPa. Next, only 6000 ml / min of a raw material gas composed of Tivol4 gas 1.5 vol%, ZrCl4 gas 1.5 vol%, CH3CN gas 1 vol%, CO gas 1 vol%, N2 gas 45 vol%, and remaining H2 carrier gas per minute Then, a titanium zirconium oxynitride film made of Ti and Zr, C, N, and O was formed by reacting at a film forming pressure of 5 kPa and a film forming temperature of 850 ° C. Subsequently, a source gas composed of ZrCl4 gas: 1.5 vol%, CH3CN gas: 1.0 vol%, N2 gas: 45 vol%, and the remaining H2 carrier gas was allowed to flow in the CVD furnace at a rate of 6000 ml / min. A zirconium carbonitride layer was formed at a film temperature of 850 ° C. and a film formation pressure of 5 kPa. A multi-layer structure including the titanium oxycarbonitride / zirconium oxide layer and the zirconium carbonitride layer as a set is used as a unit layer, and 16 sets of multi-layer structure unit layers are stacked to form a carbonitride / titanium zirconium oxide layer and a zirconium carbonitride layer. A multilayer film having a total thickness of 9 μm was formed.

  The photograph which image | photographed the cross section of the multilayer film of this invention example 1 produced in this way with the transmission electron microscope (TEM, the Hitachi make, H-800, 200 kV) is shown in FIG. FIG. 2 is a dark STEM image near the upper right portion of the center in FIG. This is an image of transmitted scattered electrons, and the atomic number effect is emphasized, and an image similar to a normal SEM image is taken. That is, the layer photographed in a bright stripe pattern is a ZrCN film, and the stripe pattern layer photographed darkly above and below it is a TiZrCNO film. FIG. 3 shows an analysis of Ti distribution in a region near FIG. 2, and FIG. 4 shows an analysis of Zr distribution. This elemental map was analyzed by an energy dispersive X-ray analyzer (EDX, manufactured by NORAN) incorporated in the TEM apparatus. 1 to 4, it can be seen that the TiZrCNO film and the ZrCN film are formed in a multilayer film with high density. No voids are observed between the films or between the crystal grains. Further, it can be seen that a large number of crystal grain boundaries penetrate between the multilayer films in a straight line, for example, from the lower right to the upper left in FIG. In FIG. 1, there are several portions that are particularly darkly photographed. This is because the lattice plane of the crystal in this portion matches the incidence of the electron beam and the electron beam is diffracted due to Bragg reflection. This is because the electron beam transmission ability is lowered. This is not because there are cracks or holes in the film.

  FIG. 5 is a high-resolution image (using HF-2100, 200 kV manufactured by Hitachi, Ltd.) in the center of FIG. A ZrCN film is photographed in the upper half of FIG. 5, a TiZrCNO film is photographed in the lower half, and a crystal grain boundary ab is photographed from the lower right to the upper left. From FIG. 5, it can be seen that both the lattice stripes of the TiZrCNO film and the ZrCN film are formed in a straight line in parallel with the crystal grain boundary ab, and are symmetrical to the left and right with respect to the crystal grain boundary ab. Recognize. That is, both the TiZrCNO film and the ZrCN film have a twin structure, and the crystal grain boundaries ab are twin planes, and this twin plane is continuous in a straight line from the TiZrCNO film to the ZrCN film. I understand that. As a result of Fourier transform of the lattice image of FIG. 5, it was found that the crystal lattice of both the ZrCN film and the TiZrCNO film is a face-centered cubic crystal, and the lattice fringes ab are {111} planes. In FIG. 5, the lattice stripes of the TiZrCNO film and the ZrCN film continue in a straight line beyond the interface (near the center of FIG. 5), and it can be seen that both grow epitaxially.

In the transmission electron micrographs of FIGS. 1 to 5, after the cross section of the film formation surface is polished to a thickness of 20 μm or less, the electron beam is transmitted through a very small area of the film cross section whose thickness is reduced by ion milling. It was taken. For this reason, it is thought that the probability that the twin part contained in the film containing zirconium and titanium and the layer formed thereon is actually observed is low. Therefore, as shown in FIG. 5, the fact that a twin portion is observed in a microscopic TEN photograph has a twin portion in a coating containing zirconium and titanium and its upper layer with a considerable frequency. It can be judged. In addition, when the sample condition is poor, such as when the film thickness of the observation sample is large, the twinning relationship may not be confirmed in the electron diffraction pattern. Also in this case, attention should be paid because the twin relation as described above may be confirmed by reworking the sample and observing the lattice image.

Five cutting tools manufactured under the conditions of Example 1 of the present invention were intermittently cut under the following conditions, and the chipping condition at the tip of the cutting edge was observed with a stereomicroscope at a magnification of 50 times, and intermittent cutting until chipping and film peeling occurred at the cutting edge. The number of times was calculated.
Work material: SCM435 material (with four grooves)
Tool shape: CNMG433
Cutting conditions: 200 m / min Feed: 0.3 mm / rev
Cutting depth: 1.5mm
Cutting fluid: Not used (dry cutting)
As a result, the product of the present invention has a sound cutting edge even after intermittent cutting up to 8000 times, no chipping or peeling, excellent film grain boundary strength and adhesion between films, and as a cutting tool during intermittent cutting. It was found that the durability was excellent.

(Example 2)
As Comparative Example 2, the following Comparative Example 2 was prepared in order to clarify the influence on the cutting characteristics in the case where the twin crystal structure is present and not present in the film containing zirconium and titanium . After a TiN and TiCNO film was formed on the surface of a cemented carbide substrate having the same composition as in Example 1 by the same method as in Example 1, then TiCl ₄ gas 1.5 vol%, ZrCl ₄ gas A source gas composed of 1 vol%, CH ₃ CN gas 0.5 vol%, CO ₂ gas 1 vol%, N ₂ gas 45 vol%, and remaining H ₂ carrier gas was allowed to flow in the CVD furnace at a rate of 6000 ml / min. Then, a titanium zirconium oxynitride film made of Ti and Zr, C, N, and O was formed at a film forming temperature of 750 ° C. Subsequently, the source gas is ZrCl ₄ gas: 1.5 vol%, CH ₃ CN gas: 0.5 vol%, N ₂ gas: 45 vol%, and the source gas composed of the remaining H ₂ carrier gas is 6000 ml / min. The zirconium carbonitride layer was deposited at a deposition temperature of 950 ° C. and a deposition pressure of 10 kPa. A multi-layer structure including the titanium oxycarbonitride / zirconium oxide layer and the zirconium carbonitride layer as a set is used as a unit layer, and 16 sets of multi-layer structure unit layers are stacked to form a carbonitride / titanium zirconium oxide layer and a zirconium carbonitride layer. Comparative Example 2 was produced by forming a multilayer film consisting of

The vicinity of the film containing zirconium and titanium of Comparative Example 2 was observed with a transmission electron microscope in the same manner as in Example 1. No twin structure portion was found in the film containing zirconium and titanium . Next, an intermittent cutting test was performed under the same conditions as in Example 1 using five cutting tools manufactured under the conditions of Comparative Example 2, and the chipping state of the blade tip was observed with a stereomicroscope with a magnification of 50 times. It was found that chipping occurred at the blade edge after both round impact cuttings and was inferior as a cutting tool. Further, when microscopic observation was performed on the part where film peeling or chipping occurred in this intermittent cutting test, it was found that film peeling occurred from a film containing zirconium and titanium, and this caused chipping. .

(Example 3)
As Example 3 of the present invention, on a throwaway tip made of cemented carbide having a composition of WC: 80% by mass, TiC: 5% by mass, (Ta, Nb) C: 6% by mass, and Co: 9% by mass. 1 and a titanium nitride film having a thickness of 0.4 μm and a titanium carbonitride film having a thickness of 1 μm were formed. Next, a source gas composed of 1.5 vol% of TiCl4 gas, 1.5 vol% of ZrCl4 gas, 2.0 vol% of CH3CN gas, 45 vol% of N2 gas, and the remaining H2 carrier gas is allowed to flow into the CVD furnace by 6000 ml per minute. By reacting at a film forming pressure of 5 kPa and a film forming temperature of 850 ° C., a titanium zirconium nitride film made of Ti, Zr, C, and N was formed. Subsequently, a source gas composed of 1.5 vol% ZrCl 4 gas, 1.0 vol% CH 3 CN gas, 45 vol% N 2 gas, and the remaining H 2 carrier gas was allowed to flow through the CVD furnace at a rate of 850 ml per minute. A zirconium carbonitride layer was formed at a temperature of ° C and a film forming pressure of 5 kPa. By stacking 12 sets of multi-layer structure unit layers, the multi-layer structure including the titanium carbonitride-zirconium layer and the zirconium carbonitride layer as a set is used as a unit layer. A multilayer film having a total thickness of 7 μm was formed. Thereafter, a source gas 2 composed of TiCl4 gas, CH4 gas, and H2 carrier gas, 200 ml / min is allowed to flow for 30 minutes, and another 20 ml / min of CO2 gas is continuously added to the source gas of this configuration for 30 minutes. By flowing, a layer (bonding film) made of titanium carbide and titanium carbonate at a film forming temperature of 950 ° C. was produced. Subsequently, AlCl3 gas, H2 gas 2 l / min and CO2 gas 100 ml / min generated by flowing H2 gas 310 ml / min and HCl gas 130 ml / min into a small tube filled with Al metal pieces and kept at 350 ° C. An α-type aluminum oxide film having a thickness of 2 μm is formed by flowing in a CVD furnace and reacting at 1010 ° C., and then a titanium nitride film having a thickness of 0.8 μm is formed at a film forming temperature of 1010 ° C. 3 coated tools were obtained.

  An X-ray diffraction pattern was measured by the 2θ-θ scanning method using Example 3 of the present invention with an X-ray diffractometer (RU-200BH) manufactured by Rigaku Denki Co., Ltd. After that, in the same manner as in Example 1, the cross section of the multilayer film of the present invention was analyzed with a transmission electron microscope (TEM, manufactured by Hitachi, H-800, 200 kV) and an energy dispersive X-ray analyzer (EDX, manufactured by NORAN). As a result of microanalysis, a multilayer film composed of TiZrCN and ZrCN is formed on the surface of the cemented carbide substrate through a TiN and TiCN film at a high density, and an α-type aluminum oxide is formed thereon via a bonding film. It was confirmed that a TiN film was formed. It was confirmed that both the TiZrCN crystal grains and the ZrCN crystal grains have a twin structure in the multilayer film portion, and that the twin planes are linearly continuous between the two crystal grains.

Using the coated tool of the present invention obtained as described above, intermittent cutting was performed under the following conditions, and the damage state of the cutting edge was observed with a tool microscope with a magnification of 50 times.
Work material: SCM435 (with four grooves)
Tool shape: CNMG433
Cutting speed: 220 m / min Feed: 0.20 mm / rev
Cutting depth: 1.5mm
Cutting fluid: Not used (dry cutting)
As a result of this cutting test, none of the products of the present invention showed chipping or peeling on the coating or alumina film containing zirconium and titanium at the cutting edge even after intermittent cutting up to 7000 intermittent cuttings. It was found that the grain boundary strength and the adhesion between the films were excellent, and the tool life was long.

Example 4
As Comparative Example 4, the following Comparative Example 4 was prepared in order to clarify the difference between the case where the film containing zirconium and titanium had a twin crystal structure and the case where the film did not have a twin structure. A TiN and TiCN film was formed on the surface of a cemented carbide substrate having the same composition as in Example 3 by the same method as in Example 3, then TiCl ₄ gas 1.5 vol%, ZrCl ₄ gas A source gas composed of 0.5 vol%, CH ₃ CN gas 0.5 vol%, N ₂ gas 45 vol%, and the remaining H ₂ carrier gas is allowed to flow through the CVD furnace at a rate of 6000 ml / min. A titanium zirconium carbonitride film composed of Ti and Zr, C, N was formed at 750 ° C. Subsequently, a source gas composed of a film forming temperature of 950 ° C., a source gas of ZrCl ₄ gas: 1.5 vol%, CH ₃ CN gas: 0.5 vol%, N ₂ gas: 45 vol%, and the remaining H ₂ carrier gas is used. A flow rate of 6000 ml per minute was passed through the CVD furnace, and a zirconium carbonitride layer was deposited at a deposition pressure of 15 kPa. By stacking 12 sets of multi-layer structure unit layers, the multi-layer structure including the titanium carbonitride-zirconium layer and the zirconium carbonitride layer as a set is used as a unit layer. A multilayer film having a total thickness of 7 μm was formed. Further, a layer (bonding film) made of titanium carbide and titanium carbonate was produced under the same conditions as in Example 2, and an α-type aluminum oxide film having a thickness of 2 μm and a titanium nitride film having a thickness of 0.8 μm were further formed. The coated tool of Comparative Example 4 was produced by forming a film.

The vicinity of the coating containing zirconium and titanium in Comparative Example 4 was observed with a transmission electron microscope in the same manner as in Example 3. No twin structure was found in the coating containing zirconium and titanium . Next, an intermittent cutting test was performed under the same conditions as in Example 3 using five cutting tools manufactured under the conditions of Comparative Example 4, and the chipping occurrence state at the tip of the cutting edge was observed with a stereomicroscope at a magnification of 50. It was found that chipping and film peeling occurred after the round impact cutting and that the cutting tool was inferior. In addition, when microscopic observation was performed on the part where film peeling or chipping occurred in this intermittent cutting test, chipping or film peeling occurred in the film containing zirconium and titanium, and this caused chipping. I understood that it was possible.

FIG. 1 shows a structure photograph of a cross section of a multilayer film of a coated tool according to an example of the present invention, observed with a transmission electron microscope. FIG. 2 shows a dark STEM image near the upper right portion of the center in FIG. FIG. 3 shows the Ti distribution in the region near FIG. FIG. 4 shows the Zr distribution in the region near FIG. FIG. 5 is a high-resolution image of the central portion of FIG. 2, showing a STEM image in which a ZrCN film is photographed in the upper half of FIG. 5, a TiZrCNO film is photographed in the lower half, and a grain boundary ab is photographed from the lower right to the upper left. .

Claims (7)

Single-layer film or two kinds of any of carbides, nitrides, oxides, carbonitrides, carbonates, nitrides and carbonitrides of the periodic table on the substrate surface It has the above multilayer coating, and at least one layer of the coating contains zirconium and titanium, the coating containing zirconium and titanium is coated with a titanium carbonitride film as a lower layer and a Zr (CN) film as an upper layer , The zirconium and titanium-containing coating , the Zr (CN) film contains crystal grains having a twin crystal structure , and the twin boundaries of the Zr (CN) film are twins of the zirconium and titanium-containing coating. A coated tool characterized by being continuous from a crystal boundary . 2. The coated tool according to claim 1, wherein the zirconium and titanium-containing film and the Zr (CN) film are laminated as a unit layer. The coated tool according to claim 2, wherein the zirconium and titanium-containing film and the Zr (CN) film are laminated in a number of 12 to 16 sets. In coated tool according to any one of claims 1 to 3, coated tool twin boundary portion constituting the twin structure is characterized in that it consists of {111} plane. In coated tool according to any one of claims 1 to 4, coated tool in which the Zr (CN) film, characterized in that it is grown epitaxially on the film containing the zirconium and titanium. 6. The coated tool according to claim 1, wherein the coating containing zirconium and titanium is made of Ti, Zr, C, and N. The coated tool according to any one of claims 1 to 6, wherein the coating containing zirconium and titanium comprises Ti, Zr, C, N, and O.